[js] funzione per input data

[raffaeu]

Ciao ho creato un funzione js che precompila una text inserendo gli /

Funzione js

<!--
	function AutoCompleteDate_DDMMAAAA(obj)
	{
		// Check if the key is a number
		var sKeyPressed;
		sKeyPressed = new String(event.keyCode);
		if (event.keyCode < 48 || event.keyCode > 57)
		{
			// don't insert last non-numeric character
			event.keyCode = 0;
		}
		else
		{
			if (obj.value.length == 2)
			{
				obj.value += "/";
			}
			else if (obj.value.length == 5)
			{
				obj.value += "/";
			}
			else if (obj.value.length > 9)
			{
			var selText = (document.all) ? document.selection.createRange().text : document.getSelection();
				if( selText.length == 0 )
				{
					// make sure the field doesn't exceed the maximum length
					event.keyCode = 0;
				}
			}
		}
	}
// -->

Parte HTML

<script language="JavaScript" type="text/JavaScript" src="../SCRIPT/funzioni.js"></script>
... ...
<form name="Info" method="post" action="registra.asp">
... ...
<input name="data" type="text" size="20" onKeyPress="AutoCompleteDate_DDMMAAAA(this);">

Mi dice errore necessario oggetto, ma con this non capisce???